OpenAI IPO closing market cap above $800B priced at 75.6% on Polymarket, up 5.6 points, on $130K traded

The Polymarket contract on whether OpenAI’s IPO closing market capitalization will exceed $800B was priced at 75.6%, up 5.6 probability points, with $130K traded, according to the supplied market snapshot published Oct 28, 2026, at 11:09 PM ET.

According to PredictionBubbles, the contract appeared among upward-moving finance markets on its movers board. That placement identifies a shift in traders’ pricing, rather than evidence of a change in OpenAI’s IPO plans.

What the board measures

PredictionBubbles ranks contracts from Polymarket and Kalshi by their absolute probability-point changes over 24 hours, updating every 15 minutes. The supplied page records a venue-data refresh at 29 Oct 2026, 03:16 UTC.

The board covers 1,982 markets that remain live for more than 14 days, excluding short-lived fixtures to limit the influence of settlement-driven swings. Its main table displays the top 150 of 516 markets that moved at least one probability point. Volume and liquidity provide context but do not affect the movement ranking.

Limits of the available evidence

The supplied page text does not reproduce the OpenAI contract’s individual card, so it does not independently confirm the headline’s price, move or volume. It also provides no OpenAI-specific news catalyst, detailed settlement terms or order-book information explaining the repricing.

Those gaps matter when interpreting the $130K traded figure. Trading volume and a probability increase describe different aspects of market activity; neither alone establishes market depth or explains why traders changed their assessment.

What it means for prediction markets

• The move is 5.6 probability points, not a 5.6% relative increase. The reported 75.6% is a market-implied probability, not a confirmed IPO valuation.
• The threshold is specific: the contract concerns an IPO closing market capitalization above $800B, rather than OpenAI’s valuation generally.
• The catalyst remains unidentified. The supplied reporting documents repricing but does not link it to an announcement, filing or other OpenAI development.
• Volume is context, not validation. The reported $130K traded does not, by itself, establish liquidity or the durability of the price move.